In data communications networks, an intermediate switching node or system is typically responsible for managing the connection between a calling node and a receiving node. This management typically includes receiving an initial call set up request from the calling node and establishing a connection to the receiving node.
Particularly in data communication networks that operate on a mobile network or indeed other data communication networks where connectivity between a node and the network is not guaranteed, call set up and call maintenance can be difficult as a node that is connected to a network at one moment may not be connected the next.
This problem has become particularly noticeable in voice over IP (VOIP) communications which typically use the Internet and other data communication backgrounds. This problem is further exacerbated by technology such as ADSL which are known to have difficulties maintaining connections when a large number of users are contending for the same bandwidth. The very nature of IP based networks means connections can be lost and re-established. Other issues such as assignment of a new IP address, NAT gateway timeout, firewall reset, changing in routing, and reset of an intermediate switch/router all can cause loss and subsequent re-establishment of a connection.
Particularly in the case of a node connected to Internet protocol (IP) based networks, it is quite common for the node to lose and immediately re-establish a connection. Not only can this happen during occasions when a node loses communication with its controlling network/switch or the like, it also happens that scheduled times when the nodes IP addressed is refreshed by its DHCP server.
In most cases, the underlying network infrastructure and applications in use are programmed or configured to accommodate these situations. However, it is much more difficult to accommodate such situations in real-time protocols and applications as the recipient is typically expecting an immediate answer/acknowledgement.